1. Field of the Invention
This invention relates to a nonflammable binder composition which comprises a special vinyl polymer emulsion and water-soluble silicate. More particularly, the invention relates to the nonflammable binder composition having excellent properties such as good adhesiveness, flexibility, storage stability and nonflammability. Furthermore, the invention relates to the nonflammable binder composition in which several advantageous properties of the vinyl polymer emulsion and water-soluble silicate are combined. The term "nonflammable composition" as used hereinafter means a composition which is hardly combustible, flame-resisting or non-combustible.
2. Description of Prior Art
In the prior art, water-dispersed vinyl polymer emulsion have been commonly employed for a wide variety of uses since they scarcely contain organic solvents and easily form coating films, and further the adhesiveness and flexibility of the coating films formed therefrom are good. Said vinyl polymer emulsions, however, mainly comprises organic components and are liable to be burnt in a fire, so that they cannot comply with the requirement of nonflammability for the construction of high-storied buildings. Further, as the formed coating film is relatively soft, it is not competent for a use in which the wear resistance is required. Accordingly, it is necessary from the industrial and commercial demands to improve the vinyl polymer emulsion by eliminating the above-mentioned disadvantages.
An inorganic binder of water-soluble silicate is also used in a coating material, adhesive agent, building material, molding material and so forth as the material to cover the defects of said organic binder. Said water-soluble silicate is employed for such uses because it has several desirable properties such as strong adhesiveness, binding property, good chemical resistance, nonflammability and high hardness, which are characteristic of the inorganic material. Although the water-soluble silicate has these advantages, it is not widely used since it has no flexibility just like the above-mentioned vinyl polymer emulsion.
Accordingly, it is industrially quite worthwhile to propose a binder having the advantageous features of both vinyl polymer emulsion and water-soluble silicate, and in view of the fact that the binder is aqueous and scarcely contains organic solvent, it is desirable from the standpoint of the prevention of environmental pollution. As a method for eliminating the brittleness of water-soluble silicate while keeping the advantageous characteristics, an organic polymer having excellent flexibility is generally mixed with the silicate. However, although the water-soluble silicate itself is stable, when a foreign material such as organic material is mixed therewith, agglomeration of siliceous material is caused to occur by neutralization of electric charges or change of pH value, or the organic material is possibly hydrolyzed during long term storage, so that it cannot be kept stable. Accordingly, it has been substantially difficult to improve the properties of water-soluble silicate by using organic polymers.